Speed ambiguity in SAR hurricane wind retrievals

1. Speed ambiguity in SAR hurricane wind retrievals Will Perrie1, Hui Shen2 and Yijun He2 1Bedford Institute of Oceanography 2Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China Recent progress on the remote sensing of ocean surface winds suggests that Synthetic Aperture Radar (SAR) is capable of giving valuable measurements of ocean surface winds with high spatial resolution and high accuracy. We focus on wind retrieval from SAR images for low- to- moderate wind conditions, as well as under high wind conditions, such as hurricanes. Examples are hurricanes Isabel (2003) and Rita (2005). Rita Isabel SAR-derived winds High wind SAR ambiguity Radar backscatter Polar grid For each of three neighboring blocks Three equations and 6 variables High wind NRCS  2 possible wind speed solutions for each NRCS. M.Powell (2006) Least-square-method Jarosz et al. 2007 QuikSCAT wind SAR wind bigger solutions SAR wind vs. QuikSCAT smaller solutions Conclusions: (1) A hurricane’s cyclonic structure, and quasi-constant wind speed equi-changing wind direction along any concentric circle allow a new wind retrieval method (2) highly accurate GMF model is needed for precise high wind retrieval from SAR (3) wind speed ambiuity is more severe at nearside of radar range, when wind blows to the radar, (based on typical hurricane structure CMOD5 and HWGMF a speed removal method is established He,Y., W. Perrie …(2005: IEEE Trans. GRS, 43, 1453-1458), Perrie, W. … (2007, in press WAF), Shen, H., Perrie … (2006 In press GRL) He, Y., Shen, H., Perrie, W., (2006 In press J. Tech.) He, Y., Perrie, W…. (2004 IEEE Trans. GRS 42, 2623-2631). final solution - NHC winds